NRf52840 custom board does not work when powered by VBUS and not found by J-link

[Vahidreza]

Hello everyone 

I have a bunch of custom dongles from the company I work for and two of them started to behave in a strange way after I tried to erase and program them through the PCA10056 board. They all are nRF52840 based dongles. The other dongles which are exactly the same, work with no problem. They all are found with nRF-Connect through PCA10056 and I can erase and program them with no problem.

The issues I'm facing with these two dongles are:

1. No J-Link can recognize the PCA10056 board when I connect these two dongles, while the other dongles are found with the exact same procedure of wire connecting. before I used to get the Error of "No J-Link Supported Board Found" (or something similar) but now that I updated the j-Link to the latest version I get the J-link dll error.
2. Both dongles have an application on their flash which work when powered through VDD. But when I power the dongle through VBUS it does not work until I put a voltage on VDD pin. Just a very short pulse on VDD makes the dongle work even when removing the voltage from the VDD pin.

Before giving the VDD pin a pulse (when trying to power the dongle through VBUS), the voltage on VDD is about 0.45V but after the pulse it rises to about 2V.

What can make these dongles behave this way after erasing and programming through PCA10056?

I've updated all the software and utilities to the latest and the OS I'm working on is macOS Monterey 12.3.1

Thank you

Vahidreza

[Kazi Afroza Sultana]

Hello Vahidreza,

The nRF52840 chip on the dongle hardware is configured in high voltage mode. This uses REG0 to lower the chip supply voltage (VDD) and the default value is 1.8 V, configured by the REGOUT0 register in UICR. This value is too low to be used with the onboard programmer on the nRF52840 DK, so erasing or programming with a firmware that does not configure the regulator for a higher VDD will leave it in a state where it can not be reprogrammed from a DK.

I think that's why you are having these issues. You can check this dongle programing tutorial (+) nRF52840 Dongle Programming Tutorial - Getting Started - nRF5 SDK guides - Nordic DevZone (nordicsemi.com) to have the idea.

Thanks.

Best Regards,

Kazi Afroza Sultana 

[Vahidreza]

Hello Kazi 

Thanks for your reply 

It looks like the problem is what you mentioned, as the voltage on SWDIO pin is less that 1V when connecting the dongle to the DK. The voltage on SWDIO pin is about 2.7V for the other dongles when connecting to the DK. 

So I need an external debug probe. But I'm confused which version is good to buy. According to the link you shared I need a programmer that adapts the logic levels to the target device. J-link Pro is offered in there. Does that mean that I can't use a J-Link Base for adapting the logic levels to the target device? I can't afford buying a J-Link Pro now, that's why I'm asking. I tried to find the differences in Segger official website but I couldn't find anything about "Adapting logic levels to the target device".

There are also some other devices with a very low price. They are called Emulators. What about them?

And please tell me if I'm right about the need of external debugger as the voltage on SDWIO pin is less that 1V when connecting to the DK. The voltage on this pin is 2.7V when not connected to the DK but it is not fixed. It sometimes drops down to 1V and sometimes to 0 also. IT IS NOT BEHAVING NORMALLY BY THE WAY. 

In conclusion: according to what I explained about the voltage on SWDIO pin, would using an external debugger help? if yes, do I have to buy a J-link Pro or the J-link Base or those cheap Emulators will solve the issue?

[Kazi Afroza Sultana]

Hello,

You can just try to power VDD with 3V while programming instead of VDDH. You should be able to program the device then. With new firmware that you are programming , you can set the REG0 output to 3V. You should be able to flash with the DK later, even when VDDH is powered. 

Thanks.

Best Regards,

Kazi Afroza Sultana